This invention relates to securing an electrical connector to a printed circuit board and in particular to a tolerance forgiving boardlock for securing an electrical connector to a printed circuit board wherein the thickness of the printed circuit board or the diameter of the boardlock receiving aperture in the printed circuit board may vary due to tolerances.
It is known to provide electrical connectors with integral means for securing the connector to a printed circuit board. The connector is temporarily secured in position on the printed circuit board by the boardlock until the boardlock and electrical connections are soldered. The boardlock holds the connector mounting face firmly in contact with the printed circuit board temporarily until permanently secured thereagainst as a result of the soldering process.
While printed circuit boards have a specified, nominal thickness, variations in thickness occur in practice. Likewise, while boardlock reciving apertures have a specified, nominal diameter, variations occur in practice. A boardlock which functions properly with a nominal thickness printed circuit board or a nominal diameter boardlock receiving aperture may fail to secure a connector on an overthickness board or be loose with an underthickness board. Similarly, a boardlock which functions properly with a boardlock receiving aperture of a nominal diameter may fail to hold a connector on a printed circuit board when the boardlock receiving aperture has a greater than nominal diameter or less than nominal diameter.
Some prior art boardlocks are designed for a specific thickness of printed circuit board and are not tolerance accommodating, such as the boardlock disclosed in U.S. Pat. No. 4,435,031. Other prior art boardlocks require tooling in addition to stuffing equipment, such as the boardlock disclosed in U.S Pat. No. 4,679,833 which requires underboard tooling to deform the portion of the boardlock extending beyond the printed circuit board, with the deformation taking place subsequent to placing the connector and integral boardlock on a printed circuit board.
A boardlock and integral spacer is disclosed in copending application Ser. No. 07/086,880, filed Aug. 21, 1987, said application is hereby incorporated by reference, in which the boardlock and integral spacer is affixed to shell members and has fingers extending for locking into apertures in a printed circuit board. Each finger is a spring member cantilevered from the boardlock body and, in one embodiment, has an outwardly tapering portion adapted to engage the bottom of a printed circuit board. The tapered portion of these fingers, therefore, engage and hold a printed circuit board of the nominal design thickness. The fail to hold a board when the thickness of a printed circuit board is near the extremes of the tolerance range, as described above. Increasing the axial length of the tapered portion would require either decreasing the angle with respect to the axis of the boardlock and integral spacer, or increasing the outward extension of the taper. Decreasing the angle decreases the force component, retaining the boardlock in a printed circuit board aperture. Increasing the outward extension would prevent entry of the boardlock through the aperture and could exceed the elastic limit of the finger as it deflects during entry into the boardlock receiving aperture.